The disclosure relates to a battery system having a plurality of battery cells which are connected to one another and having an apparatus for controlling the temperature of the battery cells, which apparatus comprises at least one hollow body, through which a coolant flows, and at least one heat conducting element having at least one first contact region and having at least one second contact region, the at least one first contact region being of planar configuration and being in thermal contact with the side face of at least one battery cell.
Batteries, such as, in particular, rechargeable lithium-ion batteries, are of great significance as energy stores, in particular in order to provide the energy which is necessary for the drive in hybrid, plug-in hybrid or electric vehicles. Lithium-ion batteries are constructed from a plurality of battery cells which are connected electrically to one another, it being possible for a plurality of battery cells to be braced mechanically with one another to produce a battery module. For safe operation of batteries of this type and for use of batteries of this type which is optimized, in particular, with regard to the performance and the service life, it has to be ensured that the batteries are used only in a defined temperature range. Thus, heating of the battery cells beyond a defined temperature has to be avoided, in particular in the case of high power input or high power output, in particular in order not to shorten the service life of the battery cells and to avoid what is known as a “thermal runaway” of the battery cells.
For this reason, the batteries or the battery cells are usually temperature-controlled. Here, battery systems which were mentioned at the outset are known which have an apparatus for controlling the temperature of the battery cells. In particular, cooling plates are used as apparatus for temperature control, a cooling plate of this type being in thermal contact via a contact area with the battery cells of the battery, in particular by the battery cells being arranged on the cooling plate. In this way, the transmission of thermal energy takes place between the contact area of a cooling plate and the battery cells. In addition, in order to improve the cooling action of the battery cells, a cooling pipe, through which a coolant flows, can be arranged below the cooling plate. A battery having a cooling plate of this type is known from document DE 10 2008 059 954 A1.
It is a disadvantage of this abovementioned type of temperature control of the battery cells that the battery cells are in thermal contact with the cooling plate only over a comparatively small area, namely the bottom area of the battery cells. However, a satisfactory contact of the battery cells with the contact area is required for a low heat transfer resistance and therefore a satisfactory transmission of thermal energy, in particular in the case of a small contact area. However, this often proves problematic, in particular since the battery cells are usually braced mechanically with one another to form a battery module, and the individual battery cells therefore frequently do not rest in an optimum manner on the contact area of the cooling plate. Here, this leads to a pronounced rise in the heat transfer resistance. Here, the problem is intensified additionally by age-induced deformations of the battery cells and by vibrations and jolts, in particular when battery modules of this type are used in vehicles. These undesired influences can even lead to individual battery cells not being in thermal contact with the apparatus for controlling the temperature of the battery cells. A sufficient temperature control of the relevant battery cells can no longer take place here, as a result of which the battery cells and, as a consequence of this, even the complete battery can be damaged irreparably. Here, the mounting of the battery cells on the cooling plate, which ensures permanently existing thermal contact between the battery cells and the cooling plate, is complicated to realize.
It is therefore desirable to improve the thermal contact of the battery cells with the apparatus for controlling the temperature of the battery cells. Document DE 10 2008 059 954 A1 has already disclosed enlarging the contact area between the battery cells and the cooling plate. In addition to the contact of the bottom area of the battery cells with the cooling plate, heat conducting plates are arranged between the battery cells, the heat conducting plates being connected thermally to the cooling plate, in order to conduct heat from the battery cells to the cooling plate.
Against this background, it is an object of the present disclosure to improve a battery system which was mentioned at the outset, in particular with regard to an improved transmission of thermal energy between the battery cells and the apparatus for controlling the temperature of the battery cells.